Infection by the human immunodeficiency virus (HIV) leads to the progressive depletion of CD4.sup.+ T cells which causes Acquired Immunodeficiency Syndrome (AIDS). Infection by the human immunodeficiency virus is typically characterized by an asymptomatic, or latent, phase of the disease. During this time, infected persons may not exhibit signs of immunodeficiency. Nonetheless, these asymptomatic, seropositive individuals synthesize virus which progressively depletes CD4.sup.+ T cells and which is infectious.
It is currently estimated that there are over one million seropositive cases with latent HIV infection in the United States today. These individuals, for whom there are no known effective treatments, are likely to progress and succumb to this disease. Therefore, a major therapeutic goal is to prolong the latent phase of HIV infection.
We have previously shown that activation of HIV gene expression is controlled by a cellular transcription factor, NF-.kappa.B (1). This transcription factor is inactive in resting T cells but is stimulated following cell activation and induces viral transcription. In addition to NF-.kappa.B, there are essential viral genes which also appear to regulate the transition from latent to active infection.
An important viral regulatory protein in HIV gene expression is Rev, an 18 kilodalton (kD) nuclear protein which controls export of viral RNA from the nucleus to the cytoplasm of infected cells. In contrast to NF-.kappa.B, the Rev protein is unique to HIV and thus unlikely to regulate essential cellular functions.
Viral replication is critically dependent on the interaction of viral gene products with host cell factors. Because viruses are intimately associated with their host cells, it has been difficult to selectively interfere with replication in vivo. Successful anti-viral approaches have selectively targeted viral gene products. For example, the treatment of herpes simplex virus (HSV) infection has taken advantage of the ability of a viral gene, thymidine kinase, to modify a drug which is toxic to the host cell. This approach led to the development of guanosine analogues, including acyclovir and ganciclovir (2-4), which are converted to DNA chain terminators only in HSV infected cells.
In HIV infection, traditional pharmaceutic targeting has thus far provided limited benefits. Although AZT has relative selectivity for viral reverse transcriptase, its toxic effect on host cell function and its low therapeutic index have provided limited protection against the progression of AIDS.
More recently, as molecular biologic studies have advanced, it has become possible to use recombinant genes to interfere with HIV gene expression. Several promising approaches have been used to exploit gene transfer to inhibit viral replication, including antisense RNA (5-7), catalytic RNA (ribozymes) (8-11), and RNA analogs or decoys (12). Viral proteins also can serve as targets for inhibition by recombinant gene products. These are well-known and contain domains which can be characterized with respect to structure and function.
Recent success in protecting cells from HIV infection using TAR analogs has provided evidence that it is possible to render cells resistant to HIV infection (12) through recombinant gene products.
The concept of dominant negative inhibition was initially described in yeast genetic systems (13). It was subsequently demonstrated that anti-viral effects could be conferred on cells susceptible to infection by herpesvirus. Using the herpesvirus VP16 transactivator, mutant proteins lacking the transactivation domain of this protein were generated which could interfere with viral replication (14).
There exists a need in the art for improved means and methods to interfere with HIV gene expression.